Archive for March, 2007

Java Generics: Instantiating Objects Of Type Parameter Without Passing Class Literal To Instance

Mar 25th

Posted by Seweryn Niemiec in [...]

9 comments

Cause generics in Java 1.5 and 1.6 are implemented using erasure, in most cases you can not get class object for type parameter, which means that in your generic classes you can not instantiate objects of type parameters. For example, the following code will not compile:

class Foo<T> {
        T field;
        public void bar() {
                field = new T(); // error
        }
}

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Java version of gstpw

Mar 23rd

Posted by Seweryn Niemiec in [...]

2 comments

jstpw
I like Java much more (about 38 times more) than C/C++. So I have written Java version of gstpw. Java version of course has more features :) and needs less lines of code to implement them. Moreover I have provided possibility to start it:

  • as standalone by $ java -jar jstpw.jat

  • via WebStart: webstart

gstpw – a simple stopwatch program

Mar 21st

Posted by Seweryn Niemiec in [...]

1 comment

screenshot of gstpw I could not find under Ubuntu any stopwatch program with modern GUI. There was only one available: “Stopwatch” by Don Libes, but it uses Tcl/Tk, so it is ugly and starts long time. Yesterday I have written new one in C. It is “one file program” which needs GTK > 2.0. Project’s home page can be found here: gstpw

How To Enable UUID In EMF Generated Model To Get Copy&Paste Working

Mar 5th

Posted by Seweryn Niemiec in [...]

4 comments

If you get very strange results using Copy&Paste in GMF diagram editor then in all likelihood your EMF model doesn’t use Universally Unique Identifiers. EMF’s XMIResourceImpl supports generation of UUID transparently but it’s disabled by default. To enable it you have to overwrite XMIResourceImpl‘s useUUIDs() method and make model plug-in use that new Resource implementation.

  1. Overwrite useUUIDs()

    2. Create new class which extends XMIResourceImpl and overwrites useUUIDs(). Put it for example in yourmodel.utils package.

    package mymodel.util;

import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.xmi.impl.XMIResourceImpl;

public class MymodelResource extends XMIResourceImpl {

        public MymodelResource() {
                super();
        }

        public MymodelResource(URI uri) {
                super(uri);
        }

        /* (non-Javadoc)
         * @see org.eclipse.emf.ecore.xmi.impl.XMLResourceImpl#useUUIDs()
         */
        protected boolean useUUIDs() {
                return true;
        }
}
  2. Prepare special ResourceFactory

    3. This ResourceFactory factory should always create instances of MymodelResource class.

    package mymodel.util;

import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.xmi.impl.XMIResourceFactoryImpl;

public class MymodelResourceFactory extends XMIResourceFactoryImpl {

        public MymodelResourceFactory() {
                super();
        }

        /* (non-Javadoc)
         * @see org.eclipse.emf.ecore.xmi.impl.XMIResourceFactoryImpl#createResource(org.eclipse.emf.common.util.URI)
         */
        public Resource createResource(URI uri) {
                return new MymodelResource(uri);
        }
}
  3. Wire new ResourceFactory with model plug-in

    4. To plug.xml of your model plug-in add extension_parser extension:

       <extension point="org.eclipse.emf.ecore.extension_parser">
      <parser
         type="gnmsmodel"
         class="com.globalus.globnms.model.gnmsmodel.util.GnmsmodelResourceFactory">
      </parser>
   </extension>

All done. Now when you modify your model and save it you will get UUID’s stored in XMI file. This will of course bread relations from GMF’a notation model. Notation model should be deleted and initialized again.

[ratings]

New Project: netdgrm

Mar 4th

Posted by Seweryn Niemiec in [...]

No comments

I have just created new project named netdgrm (code.google.com requires lower letters for projects names, so I use this convention here too). It’s simple graphical editor for diagrams of computer networks. Project’s page is here. There is a screenshot and first pre alpha 0.0.1 release. It’s very stable but lucks “few” features. Unfortunately it is a plug-in for Eclipse platform and you have to install many dependencies to get it working.

Color Scheme Generator for Charts

Mar 3rd

Posted by Seweryn Niemiec in [...]

1 comment

Sometimes one needs to show many data series on one chart. In such cases, usually distinction between those data series is achieved by using different colors for each data set. Most charting libraries leave colors selection to developer. This can be problem when there is need to choose more than six colors which can be easily distinguished by most people. Below you can find Python program which can be helpful.

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